创建项目,并导入响应的架包:
01-原生js实现ajax.html:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
//定义方法
function fun() {
//发送异步请求
//1.创建核心对象
var xmlhttp;
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();//高版本浏览器这种方式创建对象
} else {// code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");//低版本创建对象
}
//2.建立连接
/*
参数:
1.请求方式 GET、POST
GET方式,请求参数在URL后面拼接,sent方法为空参
POST方式:请求参数在send方法中定义 xmlhttp.send("username=tom");
2.请求的路径URL
3.同步或异步 true(异步)
*/
//用open方法发送请求
xmlhttp.open("GET", "ajaxServlet?username=tom", true);
//3.发送请求
xmlhttp.send();
//4.接收并处理来自服务器的响应结果
//获取方式:xmlhttp.responseText; 什么时候获取,当服务器响应成功后再获取
//当xmlhttp对象的就绪转态改变时,触发事件onreadystatechange
xmlhttp.onreadystatechange=function()
{
//判断就绪转态readyState是否为4,判断status响应的转态码是否是200
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
//获取服务器器的响应结果
var responseText=xmlhttp.responseText;
alert(responseText);
}
}
}
</script>
</head>
<body>
<input type="button" value="发送异步请求" onclick="fun();">
<input>
<!--
现在普遍运用
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>
<script>
function fun() {
axios.get("ajaxServlet","username=tom")
.then(function (value) {
console.log(value)
})
}
</script>-->
</body>
</html>
AjaxServlet:
package cn.itcast.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/ajaxServlet")
public class AjaxServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取请求的参数
String username = request.getParameter("username");
//处理业务逻辑,耗时 睡5秒
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//2.在Output 打印username
System.out.println(username);
//3.响应
response.getWriter().write("hello:"+username);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
}
输入内容
点击发送异步请求: